Abstract
The quantum-chemical calculation of iron, cobalt and nickel heteroligand complexes with the double deprotonated form of (NNNN)-donor atomic ligand—3,7,11,15-tetraazaporphine—and two oxo ligands has been carried out. Data on the structural and standard thermodynamic parameters, NBO analysis and multiplicity of the ground states of these complexes have been presented. The given calculation has been made by using the density functional theory (DFT) method with the OPBE/TZVP basis set. Based on the results of this calculation, the possibility of the existence of oxidation state VI for the chemical elements indicated above—unusual for iron and cobalt, and for nickel, unknown at all—has been shown.
Highlights
As known, the maximal oxidation state reliably found for iron is VIII [1,2,3,4] and for cobalt and nickel is IV [1,5]
In our previous works [11,12,13], using the quantum-chemical calculation by the density functional theory (DFT) method with the OPBE/TZVP basis set, we showed the possibility of the existence of zinc and
Sci. 2020, 21, 1494 basis set, we showed the possibility of the existence of zinc and copper complexes in oxidation states unusual for them; namely, Zn(III) and Cu(IV), in the inner sphere of which are such tetradentate copper complexes in oxidation states unusual for them; namely, Zn(III) and Cu(IV), in the inner sphere of (NNNN) macrocyclic ligands as 3,7,11,15-tetraazaporphine and phthalocyanine, in which are such tetradentate (NNNN) macrocyclic ligands as 3,7,11,15-tetraazaporphine combination with one or two monodentate ligands having donor atoms with high electronegativity, and phthalocyanine, in combination with one or two monodentate ligands having donor atoms with namely F
Summary
The maximal oxidation state reliably found for iron is VIII [1,2,3,4] and for cobalt and nickel is IV [1,5]. It is well known that stabilization of oxidation states uncharacteristic for any particular d-element can be achieved using complexing processes with certain specific polydentate (and, in particular, macrocyclic) ligands. Among these ligands, macrocyclic organic compounds containing four donor nitrogen atoms, each of which is capable of forming a chemical bond with different atoms of p-, d- and f -elements, are very promising for solving this problem. In particular [6,7,8,9,10], such ligands include porphyrin, 3,7,11,15-tetraazaporphine (porphyrazine) and their alkyl, aryl, and halogen derivatives, capable of stabilizing, in principle, both abnormally-high and abnormally-low oxidation states of various d-elements
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